If you want to sell the whole thing (coin+balance) then sell it the same way you'd sell any other
physical item... Ebay, craigslist, the collectibles section here on Bitcointalk etc...
If you're just wanting to cash out the BTC, then Ebay isn't an option. You'd need to expose the private key on the coin, import that into a wallet and then send the balance to an exchange. For a wallet I would suggest
Electrum or
Wasabi... can't really comment on exchanges as there are a number of issues around location/country etc.